Environmental benefits of digital over paper: A wayfinder case study

Wayfinder enables patients to view and manage their referrals and appointments digitally, reducing the need for paper communications and helping deliver the NHS’s broader sustainability objectives. This includes a material reduction in the carbon footprint associated with physical letters and postal logistics, achieved through secure and scalable digital infrastructure.

Wayfinder exemplifies how digital innovation, when designed and implemented with sustainability in mind, can deliver meaningful environmental benefits while also supporting better care outcomes and system resilience.

Digital transformation offers significant environmental benefits that align with NHS sustainability objectives whilst enhancing overall public health outcomes.

Digital channels enable resource efficiencies and reduction of environmental impact by reducing waste and replacing physical processes like travel and paper-based communications with lower carbon emitting alternatives.

However, the digital industry is also a significant contributor of global carbon emissions; data centres alone contribute more carbon dioxide equivalent (CO2e) per annum than the entire aviation industry. With continuous developments in virtual reality and high-resolution images and the emergence of artificial intelligence, the impact of digital is projected to increase.

Low carbon software and application design is a new area of focus. As responsible digital leaders and citizens it is incumbent on us to build a more mature understanding of the relationship between our impact on the environment and how climate change is likely to impact on the stability of digital services and thus their potential to bring wider resilience to the health system.

Greener NHS is the NHS response to the climate challenge with a focus on decarbonisation by 2045. The Greener NHS Vision is “To deliver the world’s first net zero health service and respond to climate change, improving health now and for future generations”.

With around 4% of the United Kingdom’s carbon emissions, and over 7% of the economy, the NHS has an essential role to play in meeting the net zero targets set under the Climate Change Act (Delivering a ‘Net Zero’ National Health Service

Greener Digital takes a ‘net-gain’ perspective on digitisation well managed digitisation unlocks multiple benefits including sustainability and net-zero improvements; architecting for sustainability ensure we are not eroding the benefits enabled by digitised healthcare.

This web page provides an example of the benefits that can be achieved when considering the impacts and benefits of digital transformation from an environmental perspective. We hope to inspire others to collaborate and share lessons and good practice. We are also pleased to share our findings and carbon equivalent calculations that can be utilised across the NHS for carbon measuring and reporting. We welcome your feedback, comments and suggestions and look forward to sharing more and collaborating further with this community.

In September 2021, NHS England approached NHSX to explore the feasibility of providing patients with direct access to their referral and appointment information in the NHS App or NHS website for those waiting for elective care. This led to the creation of the Wayfinder NHS App service.

Wayfinder leverages national digital channels (NHS App both in mobile and web formats, NHS login, the NHS e-Referral Service, a new NHS England Patient Care Aggregator (PCA) and trust systems, such as Patient Engagement Platforms (PEPs)) to provide users with a simple and secure way to manage their care information.

In September 2022, Wayfinder went live in three NHS acute trusts with the core functionality of enabling users to view and manage their referrals and appointments via the NHS App.

As of April 2025, 114 NHS trusts are now connected to the NHS App, with 12 PEP suppliers, and the service has been used over 130 million times.

In parallel to increasing the coverage of Wayfinder across England, the service continues to surface additional features in the NHS App including Notifications and Messaging, Documents, and Questionnaires. These additional features enable app users to receive appointment reminders, view appointment letters, and complete pre-appointment questionnaires. Wayfinder is currently delivering a phase 3 scope that includes allowing users to select their paperless preferences and view their past appointments, as well as improving management information and analytics, surfacing inpatient and day case appointments in the NHS App, and extending coverage to mental health trusts.

Wayfinder is having a positive impact on helping trusts reduce waiting times and missed appointments or did not attend (DNA) rates; it has also increased traffic to the NHS App, and is now consistently the second most used service after viewing a health record, with 21% of app users viewing and managing their referrals and appointments in March 2025.

The Patient Care Aggregator (PCA) is the ‘engine’ that enables the sharing of information held in Trust systems so that it can be viewed via by patients via the NHS App. According to Amazon Web Services’ (AWS) official metrics, the emissions created due to the storage and processing of data in the PCA were under 0.1 tCO2e (tons of carbon emissions), given Amazon’s power purchase agreements and purchase of renewable energy credits. AWS report the PCA to be Net Zero, naturally we wanted to interrogate this statement. 

The wayfinder screens 

The NHS produces 158 million letters annually. The average letter consists of 2 x A4 Sheets of paper, an A5 envelope and uses second class postage.

Each letter requires an envelope, stamps and resources to deliver the letters. Reducing the number of printed letters will also reduce CO2e relating to production of paper, printers and inks. 

The updated benefits case of Wayfinder estimates that the uptake of elective care digital appointment letters via the NHS App is expected to avoid the use of up to 30 million printed A4 sheets of paper per annum, which equates to 6,635 tCO2e removed per year.

The NHS did not previously have a carbon equivalent calculation for a physical outpatient appointment letter. There was no CO2e measurement for the NHS to produce and deliver outpatient appointment letters.

Ben Tongue, Greener Digital Lead, approached Leeds University School of Geography to recruit a student via a Professional Placement Scheme. Luke Mincin carried out our full boundary carbon footprint analysis of the impact of an outpatient appointment letter.

Through responses to a trust survey, the Greener NHS calculated that an average of 48g of CO2e is emitted every time a trust posts a patient appointment letter.

The model assumes the average letter consists of two A4 sheets of paper, which are mixed between virgin and recycled paper. The letter is posted in an A5 envelopes using second class postage. It is assumed that there are no additional leaflets or other items enclosed in the letter and that there have been no clinical copies printed and stored.

An appointment letter is posted every time an appointment is confirmed. An additional letter is posted should the appointment be cancelled. A third letter is posted should the appointment be rescheduled. On average, 1.5 letters are posted for every patient appointment. This means an average of 72g of CO2e is emitted per appointment. That is almost the same footprint as an NHS Apron (65g) or a duckbill FFP respirator (76g CO2e).¹

The community of industry and academia within the Accelerated Capability Environment (ACE), a UK government initiative, is known as the Vivace Community, of which Servita are a member. ACE began working with NHS in relation to an Application Programming Interface (API) Aggregator that was aimed at helping alleviate the elective care backlog in late 2021.

Through the ACE community, Servita were engaged in January 2022 by NHS England to build a health information exchange, patient consent engine and national API integrations to provide patients with an end-to-end view of their care pathways on a single screen in the NHS App. The service Servita built to do this is called the Patient Care Aggregator (PCA).

The PCA benefits from a stateless architecture which queries and processes trust data in real time minimising the need for storage.  The PCA leverages Kubernetes to achieve horizontal auto-scaling, ensuring the compute power provisioned does not exceed that which is required.

Further optimisation of compute power is achieved using a NodeJS codebase. NodeJS is commonly regarded as the most performant code base available and was therefore chosen to yield a platform that can efficiently deliver a national service in line with a sustainability agenda.

The PCA is cloud-hosted on Amazon Web Services (AWS) and was architected to adhere to the sustainability pillar of AWS’s Well-Architected Framework, adopting a “minimise compute” philosophy to aggressively mitigate carbon emissions by treating compute as a privilege, not a right². 

This philosophy guided most architectural choices, including: 

• the adoption of a stateless architecture, avoiding duplicating data in a centralised store in favour of relying on local data stores and thus avoiding significant compute overhead typically associated with data storage
• the “right-sizing” of compute resources to demand, using Kubernetes and horizontal auto-scaling to ensure that compute resources are decreased as demand decreases overnight
• the use of schedulers to automatically deactivate non-production compute resources overnight, or after a period of inactivity
• the provision of a single, shared development cluster to avoid the excess compute caused by developers running code in a local development environment

• the right-sizing of non-prod environments, scaling test environments to use production-level compute resources only when required for performance testing

• the use of serverless technologies where appropriate, including lambda functions and managed services, to avoid excess compute caused by provisioning dedicated virtual machines or servers 

• use of "tree shaking" to ensure all dependencies are required and to remove dead code, ensuring minimal carbon emissions by reducing bundle size for storage and network transmission, while ensuring a lean application that uses only the compute resources it needs to run

Validating PCA carbon emissions

Greener NHS engaged “Greenpixie” an impartial, cloud emissions specialist to conduct a thorough assessment of the PCA’s carbon usage data from July 2023 to April 2024.

Total carbon emissions and savings

During the analysis period, the Wayfinder application's total cloud carbon emissions were 1.8 tonnes of CO2e. By transitioning from paper-based letters to digital communications, Wayfinder enabled the avoidance of 1.96 million letters, resulting in a significant carbon saving of almost 100 tonnes. This figure includes the operational carbon of the AWS platform.

The per transaction carbon impact of the PCA is 1.37g CO2e.

Greenpixie reported that after the implementation of the Wayfinder platform, carbon emissions per appointment letter dropped to 0.057g per appointment A total of 2.83 million Wayfinder documents were opened during the period. Using this as a proxy for appointments, the average carbon per Wayfinder document was calculated at 1.6g, demonstrating a 97.8% reduction in carbon compared to sending physical letters.

A patient engagement platform is a digital tool that allows patients to access their health information, communicate with their healthcare team and manage their appointments.

Patients Knows Best (PKB) is a social enterprise and certified B Corporation. which has been net zero since 2021. As of September 2024, PKB has supported over 3.5m letters being sent digitally, rather than physically, avoiding 168t CO2e. 

PKB used the following method to calculate the carbon footprint of a Wayfinder patient transacting on their platform:

The following calculations are based on a PKB patient using Wayfinder to manage their appointment and using the models explained in this web page.